Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$108.94	3.644%	$112.9098	$112.91	$112.90	$112.90
Purchase #2	$158.75	13.485%	$180.1574	$180.16	$180.15	$180.20
Purchase #3	$37.74	12.805%	$42.5726	$42.57	$42.55	$42.60
Purchase #4	$123.53	6.753%	$131.872	$131.87	$131.85	$131.90
Purchase #5	$179.47	4.120%	$186.8642	$186.86	$186.85	$186.90
Purchase #6	$162.52	12.144%	$182.2564	$182.26	$182.25	$182.30
Purchase #7	$194.36	9.767%	$213.3431	$213.34	$213.35	$213.30
7 purchase totals =	$965.31		$1,049.9755	$1,049.97	$1,049.90	$1,050.10